In general thermal desorption is limited to material with relatively high vapor pressure and a molecular weight of less than 500 Da. The lack in compound coverage in the types of molecular species that can be detected intact by mass spectrometry makes thermal desorption less of a universal surface sampling approach than laser based desorption approaches that have a much more broad compound coverage and are able to desorb polymers and proteins intact from a surface. However, laser desorption (nanosecond and picosecond pulse length laser ablation) at its core is inherently a thermal desorption process that happens on a very fast time scale 108 to 1013 K/s and is commonly referred to as laser induced thermal desorption (LITD). Spatially resolved thermal desorption processes are described in Jesse et al U.S. Pat. No. 8,384,020 the disclosure of which is incorporated fully by reference.
Prior work has demonstrated that applying sufficiently high heating ramp rates to a tungsten wire filament will allow intact desorption of large biomolecules such as substance P, as well as melettin and valinomycin. See Anderson, W. R.; Frick, W.; Daves, G. D.; Barofsky, D. F.; Yamaguchi, I.; Chang, D.; Folker, K.; Rosell, S. “Mass Spectra of Underivatized Peptide Amides related to Substance P.” Biochem. Biophys. Res. Commun., 1977, 78, 372-376, and Karbach, V.; Knochenmuss, R.; Zenobi, R. “Matrix-Assisted Filament Desoption/Ionization Mass Spectrometry.” J. Am. Soc. Mass Spectrom., 1998, 9, 1226-1228.
The difficulty of reaching higher heating rates stems from the challenge of applying a voltage to the resistive element in a short enough times scale to heat it up to significantly high temperatures. Prof. William King at the University of Illinois-Urbana Champagne, who pioneered the technology behind the use of the thermal probes, has been able to heat cantilevers to over 833 K within 16 μs, by using electronics that have the power required to drive cantilevers at high speed and high power. See Lee, J.; Beechem, T.; Wright, T. L.; Nelson, B. A.; Graham, S.; King, W. P. “Electrical, Thermal, and Mechanical Characterization of Silicon Microcantilever Heaters.” J. Microelectromech. Syst. 2006, 15, 1644-1655. The disclosures of all of the above references are hereby incorporated fully by reference.